TG68 - The Open Source Minimig CPU into the FPGA

[alexh]

Excellent work. I am glad you were able to release your work.

Is there any attempt to make the instruction timings the same as the original 68k?

Why do I ask?

It's just that some programs rely on the timing of the 68k instructions relative to the rest of the Amiga hardware.

Compatibility is as important than speed IMHO.

It is a million times worse for the Atari ST where there were no accelerators and standard 68k CPU instruction timing was the core to everything. A large % of ST games rely on it.

[alexh]

TobiFlex wrote:
this is version 1.0!

I understand and I take my hat off to you.

There are some subtle undocumented 68k behaviour that you might be interested in:

http://www.trzy.org/files/68knotes.txt
http://pasti.fxatari.com/68kdocs/

[alexh]

Interesting.

Try this program

http://amiga.nvg.org/warlock/adf/b/Birk+Sundell/100C64Tunes.adf.gz

It is known to be sensitive to 68000 incompatibility. I dont think it will work, but if it does, then great!

The Hardwired demo times the 68000 multiply instruction and if it is not a time it expects it comes up with: "This demo don't like Axel". (Axel = Accelerator)

[alexh]

TobiFlex wrote:
Do you know a .ADF Source from the hardwired demo?

http://www.filefactory.com/file/8bef63/

FYI: you can convert DMS to ADF using the xDMS tool

http://zakalwe.fi/~shd/foss/xdms/

[alexh]

It doesnt have enough bits going to the VGA port to do Amiga gfx.

[alexh]

Hans_ wrote:
This is great progress. That's one less IC that needs to be soldered in.

Hardly, you need to reread Dennis's post I think the results show that the TG68 takes up about 70% of the MiniMig v1.x FPGA, leaving no room for MiniMig :-(

I am sure TobiFlex could get the size of the TG68 down abit with some good constraints and if he made some of the instructions multi-cycle.

[alexh]

TobiFlex wrote:
I will not optimize the size next time.
I will only optimize the function and speed next time and I think I need more LCs for the optimized Design.

As Jens Schoenfeld of Clone-A said (and from experience I agree) when reverse engineering, the more you improve compatibility the smaller the design sometimes gets. You start to get closer to the original design which was inherently smaller.

Good luck and as soon as I get a board I'll help out a bit. Come on Crom!

[alexh]

tonyyeb wrote:
can someone explain why a simpleton like me who just wants a Minimig and future Minimig developments to continue... should be getting excited?

If you have a MiniMig v1.x board you dont care.

If are a potential MiniMig v1.x owner, but cannot find one cos no one makes them, and were considering getting buying one of the slightly expensive off the shelf Altera DE1 or DE2 boards then you are wetting your pants as a more compatible DEx-MiniMig is on it's way.